Simple method to select a pit in the presence of grade uncertainty

Mining Engineering , 2013, Vol. 65, No. 12, pp. 63-66

Elkington, T.; Prott, R.

Mine planners must select a single pit for design with the knowledge that the grades on which this selection is made are uncertain. This uncertainty is often ignored through the use of deterministic models of grade. This makes the mine planner’s job simpler but does not necessarily lead to the “correct” or “best” selection. Grade uncertainty is typically modeled with conditional simulation, which generates multiple possible realizations of grade that are equally probable (or improbable). Methods for incorporating grade uncertainty into mine planning to date have either been perceived as being too complicated, not accessible or too time-consuming. This paper proposes a simple and efficient modeling approach to incorporating conditional simulation into pit optimization, which would be able to be applied in currently commercially available software. An example for Resolute Mining Ltd.’s Syama gold project in Mali shows the range of ore, grade and value outcomes associated with generating pits through a variety of methods.